- (void)xmppRoomDidJoin:(XMPPRoom *)sender
{
/**
* You can read from an array containing participants in a for-loop
* and send multiple invites in the same way here
*/
[sender inviteUser:[XMPPJID jidWithString:@"keithoys"] withMessage:@"Greetings!"];
}

There, you've created a XMPP multi-user/group chat room, and invited a user. :)